There is disclosed an outdoor unit comprising a case provided to define an exterior design and comprising a plurality of side panels having an inlet hole providing a path for sucking external air, a base plate supporting the plurality of the side panels, an upper panel having an outlet hole for discharging the external air sucked via the inlet hole to the outside; a heat-exchanger provided in the case and configured to exchange heat with the external air sucked via the inlet hole; a sliding plate slidingly provided in the base plate and supporting the compressor module and movable via the opening to expose the compressor module outside the case; and a compressor module configured to supply a refrigerant that exchanging heat with the external air to the heat-exchanger, such that the compressor module may be manipulative outside and demounted when the sliding plate is located in the exposure position.